Previous studies suggest that insurance status may play a role in utilization and outcomes for patients with critical illness. However, the mechanism for this effect is unclear, and the impact of health insurance expansion on critical care utilization is unknown (1-5). Massachusetts initiated statewide insurance reform in 2006 with the goal of near-universal insurance coverage, decreasing the rate of uninsured state residents from approximately 7.5% to less than 3% within three years (6). This legislation served as a model for the Patient Protection and Affordable Care Act passed by the United States Congress in March 2010. Near-universal health insurance coverage is unprecedented in the United States and it is critical to understand the impact of health insurance reform on critical care service utilization. This proposal outlines a plan to utilize the natural experiment of reform in Massachusetts to examine and help anticipate the impact of national health insurance reform on critical care delivery. In Aim One I will determine the relationship between Massachusetts insurance reform and intensive care unit admission rates. In Aim Two I will determine the relationship between Massachusetts insurance reform and total hospital length of stay in patients with critical illness. Both aims will use state discharge data available from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project, comparing hospital admissions over time in Massachusetts to several control states using a difference-in-differences approach. In addition to addressing these research aims, over the course of this fellowship I will engage in a rigorous training program of didactic course work and close research mentoring by senior health services researchers, health economists, clinical epidemiologists and biostatisticians. Throughout the conduct of this study and training plan, I will gain skills that will allow me to mature as an investigator and compete for a K series career development award. Ultimately, this NRSA fellowship opportunity will enable me to make significant contributions to the fields of health services research and critical care medicine through insights into the impact of health insurance reform on critical care utilization. This research will facilitate the anticipation of resource allocation needs, and better inform discussions of health care reform. PUBLIC HEALTH RELEVANCE: The clinical and economic burden of critical illness in the United States is enormous-over 5 million Americans are admitted to an intensive care unit each year, with costs approaching 1% of the gross domestic product. This project will generate novel insights into the role of health insurance reform on critical care utilization and provide an opportunity for the primary investigator to develop into an independent researcher in the field of critical care health services research.